用视诱发电位和富里叶变换作视力客观估计

目的:研究用图形视觉诱发电位(PVEP)和离散富里叶变换(DFT)作视力客观估计的方法。方法:检测对象为33只正常眼。用翻转频率为10次/秒,条纹张角分别为30、20、18、12、10、6、4和2弧分的垂直方波光栅图形刺激,记录相应的稳态图形视诱发电位。用离散富里叶交换提取WEP频谱中10Hz成分的幅值。以光栅条纹张角为横坐标、相应的VEP频谱幅值为纵坐标作关系曲线,取阈值附近的近似线性部分的数据点作直线回归,用外推法求得阈值和视力。结果:比较VEP所测之视力与用国际标准视力表所测之视力,可见在本研究中70％的受检眼VEP视力估计较准确。结论:用本研究中的VEP技术客观地测量视力可靠性较高。眼科学报1997;13:59～61。

Objective Assessment of Visual Acuity with Visual Evoked Potential

Purpose :To study the technique for objectively assessment of visual acuity with Pattern Visual Evoked Potential (PVEP)and Discrete Fourier Transform (DFT). Method:Thirty-three normal eyes were tested in this study. Reversal square-wave gratings of eight different sizes (30,20,18,12,10,6,4,2 min. of arc) were used as stimuli. The reversal rate of the stimuli was 10 times/sec. The harmonic amplitudes of VEP at 10 Hz were calculated with Discrete Fourier Transform. A relation curve between the harmonic amplitude and the size of grating was plotted from the data of each tested eye. Regression line was fitted to the data points in the approximately linear section of the curve which is near the threshold of zero amplitude. The threshold of the grating size was obtained by extrapolating of the regression line to zero amplitude, and the visual acuity was assessed with the threshold. Result : In seventy percent of tested eyes, the visual acuities assessed with VEPs were consistent with those measured with the International Standard Test Chart. Conclusion :The VEP technique for visual acuity assessment is reliable. Eye science 1997 ; 13 :59 -61.